Some multi-channel MCM IC devices have at least 2 paths per channel, where a path failure in one channel does not affect functionality of the device and there is no conventional measured test parameter that can reflect the path failure. Isolated gate driver ICs, such as capacitively isolated ICs, is one example of such devices. A gate driver is a power amplifier that accepts a low-power input (e.g., a pulse-width modulation (PWM) input) from a controller IC and produces a high-current drive input for driving the gates of high-power transistors such comprising an Insulated Gate Bipolar Transistor (IGBT) or power metal-oxide-semiconductor field-effect transistor (MOSFET).
In operation isolated gate driver ICs receive a control signal and send the signal across an isolation barrier to drive the power devices. Such gate driver ICs are generally a MCM solution with TX (transmitter) die and at least one RX (receiver) die on respective sides of isolation barrier. Capacitive isolation is a relatively new technology that can be used for the isolation barrier. There are 2 inter-die bond wires connecting pins on the TX die to pins on the RX die for each channel as a differential bond wire per channel is known to provide better noise immunity. Capacitive isolation technology uses differential (both positive and negative) isolation capacitor for better noise immunity.
The signal transmission from the TX die to RX die fails if both inter-die bond wires are missing or are otherwise causing an open circuit condition. However, if only one of the bond wires is missing (or is open), signals can still be passed by the other bond wire to the output of the gate driver, but with somewhat degraded noise immunity. Known test solutions to this problem include using additional noise immunity tests or other tests to check whether there is any inter-die bond wires missing or open, and X-ray imaging (see FIG. 4B described below).